The invention relates to the field of electrical circuit breakers designed to open automatically upon the occurrence of an overload; and in particular to arc-energy-limiting magnetic blow-out breakers designed to interrupt fault currents which are high for the size of the breaker.
Magnetic blow-out breakers have been widely used for many years. The desire to miniaturize and to add features such as remote operation has caused designers to refine the techniques for blowing the arc into an arc chute, where the arc is broken into many short arcs so that is quickly extinguished. This has led to the development of arc runner and booster loop structures, which cause the termination point of one end of the arc to transfer from one of the contacts to an arc runner, and to be driven down the runner toward and into the arc chute by magnetic forces acting on the arc.
In order to increase the forces acting on the arc, a booster loop has been proposed, in which an extra conductor portion carries the current along a path which adds to the magnetic force acting on the arc. One such construction is found in the Weber model AS168 breaker, which includes internal connections from the movable contact armto a booster loop element which carries current past the arc runner in the same direction as the arc current.